Fluid pumps are used in hydraulic systems to circulate fluid under pressure to various hydraulic components. For instance, conventional vehicles typically use an engine-driven fluid pump to circulate transmission fluid to various clutches, cooler systems, and other points of use within a powertrain. A supply of the fluid is retained in a sump at a low point of the powertrain. The pump draws the fluid from the sump and moves the fluid through the various fluid paths of the vehicle's hydraulic system. Engine-driven pumps quickly spin up after engine start to move this fluid to where it is needed in the system.
In a hybrid electric or a battery electric powertrain, the engine-driven pump may be accompanied or replaced by an electrically driven pump. Hybrid electric powertrains may use an electric pump to augment the functionality of the engine-driven pump, e.g., during engine off periods. Other hybrid electric powertrains, as well as battery electric powertrains, may eliminate the engine-driven pump altogether. Electric pumps are considered to be torque-limited relative to the levels of torque generated by engine-driven pumps, which is largely a result of physical limits on the electrical current that the pump can receive.